The Pen Llŷn a’r Sarnau SAC is located in northwest Wales (click here for map). It is one of the largest of the marine SACs in the UK, straddling almost 230km of coastline and covering an area of about 146,023 hectares. The site extends from Penrhyn Nefyn on the north coast of the Llŷn to the mouth of the Afon Clarach (Clarach River) about a mile north of Aberystwyth on the west Wales coast.
The seaward boundaries of marine SACs are drawn as close as possible to include the qualifying interests, but in straight lines between landmarks or buoys or in open sea areas to ensure ease of marking on navigational charts. Where intertidal areas are included in the Pen Llŷn a’r Sarnau SAC the landward boundary of the SAC has been drawn to encompass the wildlife habitats / species of the site – in these cases the landward boundary varies around the coast and may follow a coastal feature such as a fence/wall or top or bottom of coastal slope or it may follow the mapped limit of high water or the top of mapped vegetation limits along a cliff. Where intertidal areas are not included in a marine SAC the landward boundary generally follows mean low water. The intertidal areas included are considered to be integral to the marine conservation interest of the site, and essential components of the features for which the site has been selected.